Oil-in-water emulsions have various uses in the pharmaceutical field. They typically include an aqueous carrier, a biocompatible oil, and a biocompatible surfactant which stabilises the oil droplets.
Reference 1 discloses containers for emulsions, and suggests that the emulsions can include krill oil. Reference 2 discloses pharmaceutical compositions for parenteral administration which comprise krill oil phospholipids in an oil-in-water emulsion, and reports that these emulsions are physically more stable than equivalent emulsions based on egg phospholipids, but it does not report how its emulsions were made. Reference 3 describes further parenteral emulsions which are based on krill phospholipids and include hormones. These emulsions are prepared by dissolving the hormones in an oil, and emulsifying this oil into an aqueous phase together with the krill phospholipids. Reference 4 discloses oil-in-water emulsions which include krill oil as an active ingredient. These emulsions were made by mixing krill oil and soybean oil, and then combining this mixture with an aqueous lecithin solution.
Krill oil is gaining attention as a source of omega-3 fatty acids. Omega-3 fatty acids from natural sources are found predominantly in the form of triglycerides and phospholipids. Phospholipids generally comprise one or two fatty acids groups bound to a phosphate group, usually via a glycerol backbone. The phosphate group is further linked to an organic headgroup, such as a choline or ethanolamine group. In addition to glycerol-derived phospholipids, the term “phospholipid” also encompasses sphingomyelin. Krill oil is distinguished from other sources of omega-3 fatty acids by a high proportion of fatty acids in the form of phospholipids, which may constitute as much as 60% by weight of the oil.
In addition to phospholipids and triglycerides, krill oils also naturally contain astaxanthin, and references 2-4 take advantage of the antioxidant properties of this molecule in order to ensure stability of their emulsions e.g. reference 4 used a krill oil containing 0.095% astaxanthin, and the emulsions in reference 2 included 0.04 g/L astaxanthin. In addition to astaxanthins, the krill oil in reference 4 contains high levels of vitamins A and E (18437.5 IU and 4.2 g per 100 g, respectively). The emulsions also contain oleic acid and/or sodium oleate.
It is an object of the invention to provide further and improved oil-in-water emulsions using phospholipids from krill oil, and methods for their preparation.